JP3161866B2 - Manufacturing method of optical fiber coupler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical fiber coupler for use in optical communication and optical sensors.

[0002]

2. Description of the Related Art In an optical fiber communication system, an optical fiber coupler is used as an important component for branching, coupling, demultiplexing, and multiplexing light. In particular, an optical fiber coupler obtained by processing an optical fiber is used in many fields because of its excellent coupling with an optical fiber and low loss of transmitted light.

[0003] In an optical fiber coupler, a plurality of single-mode optical fibers are bundled, a part thereof is fusion-stretched to form an optical coupling portion, and light incident on one of the plurality of optical fibers is transmitted. Branches to another optical fiber at a constant branch ratio.

FIG. 2 is a view showing a main part of a method for manufacturing an optical fiber coupler. The optical fibers 1 and 2 are fixed in such a manner that the protective coating material 3 is removed in advance from the portions to be fused, and the clamps 4 and 5 are in contact with each other. The clamps 4 and 5 include a screw rod 22 and a guide rod 23.
And a pulling mechanism including a driving motor M. The contact portion between the optical fibers 1 and 2 is heated by an oxyhydrogen flame 6 to fuse the two optical fibers 1 and 2 together. Here, when the drive motor M is rotated, the clamps 4 and 5 move in the directions indicated by the arrows, and the optical fibers 1 and 2 are stretched in the axial direction to form the tapered optical coupling portion 11.
At this time, light of a predetermined wavelength is incident on the optical fiber 1 from the light source 7, the output light amount from the optical fiber 1 is detected by the photodetector 8, and the output light amount from the optical fiber 2 is detected by the photodetector 9. When the desired branching ratio is reached, the drive motor M is stopped to stop the stretching. In the fusion-stretched product of the optical fibers 1 and 2 obtained as described above, the tapered optical coupling portion 11 is extremely thin and has low mechanical strength. The branching ratio changes and the operating characteristics become unstable. For this reason, the fusion-stretched product of the optical fibers 1 and 2 is bonded and stored in the protective member so that no external stress is applied.

[0005] The optical fiber coupler manufactured in this way must be such that its characteristics are not degraded by the adhesive storage in the protective member. In order to stabilize the characteristics, Japanese Unexamined Patent Publication No. 3-107111 discloses an optical fiber coupler in which the Young's modulus of the adhesive is limited to a specific range, and the fused stretched optical fibers 1 and 2 are fixed. A method is disclosed.
Japanese Patent Application Laid-Open No. 3-168709 discloses a method of manufacturing an optical fiber coupler by fixing a fusion-stretched product of optical fibers 1 and 2 with an adhesive having high heat resistance and a low coefficient of thermal expansion. .

[0006]

However, even with the methods described in these publications, the excess loss of the optical fiber coupler increases after the fused and stretched product of the optical fibers 1 and 2 is bonded and stored in the protective member. I could not control that. As a result, the yield of products has been reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended to manufacture an optical fiber coupler which does not deteriorate its properties even if the fusion-stretched product of the optical fibers 1 and 2 is bonded and stored in a protective member. The aim is to provide a method.

[0008]

To achieve the above object, a method for manufacturing an optical fiber coupler according to the present invention comprises:
As shown in FIGS. 1 and 2, a plurality of optical fibers 1 and 2 are bundled, a part of them is fused and stretched while being heated to be optically coupled, and then sandwiched between at least two quartz protective members 17.
In the method of manufacturing an optical fiber coupler in which the protective covering material is removed before and after the optical coupling portion 11 of the optical fiber , the protective member 17 is coated with an adhesive 16 having a viscosity of 1000 to 50,000 cps at 20 ° C. It is characterized by being adhered to.

[0009]

After the optical fiber coupler is heated and melted and stretched and optically coupled, the optical fiber coupler is sandwiched between quartz protective members 17 before and after the optical coupling portion 11.
And store it. At that time, the viscosity is 1000 ~ 50,000 cps
Since the adhesive 16 is used, the optical fiber coupler has almost no change in the characteristics of the branching ratio and the excess loss before and after the bonding and storage. In addition, the adhesive strength becomes sufficient.

If the viscosity of the adhesive 16 is 1000 cps or less, the adhesive 16 easily penetrates, but excessively penetrates into the meeting surface of the optical fibers 1 and 2 by capillary action, thereby securely fixing the front and rear of the optical coupling portion 11. As much as possible amount does not remain in the necessary places, and the adhesive strength is insufficient. In addition, the adhesive 16 flows to the optical coupling portion 11, and the fusion-stretched product of the optical fibers 1 and 2 is deformed by the stress generated until the adhesive 16 is cured, and the branching ratio fluctuates. If the viscosity of the adhesive 16 is 50,000 cps or more, the adhesive 1
6 is insufficiently penetrated into the adhesive surface, resulting in non-uniform application, and also causes non-uniform stress applied to the optical coupling portion 11 during curing.
The fusion-stretched product of the optical fibers 1 and 2 is deformed, and the branching ratio fluctuates. In addition, the adhesive 16 is insufficiently penetrated, resulting in insufficient adhesive strength.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing an optical fiber coupler to which the present invention is applied will be described below in detail with reference to the drawings.

FIG. 1 is a side sectional view of an embodiment of an optical fiber coupler manufactured by a manufacturing method to which the present invention is applied, and FIG.
It is a longitudinal cross-sectional view.

FIG. 2 shows an embodiment of a method for manufacturing an optical fiber coupler to which the present invention is applied.

First, an embodiment will be described with reference to FIG.
Optical fibers 1 and 2 (125 μm in diameter) are attached to a device for fusion drawing. The device has clamps 4 and 5 for holding two places of the optical fiber and pulling them in opposite directions, and a burner for obtaining an oxyhydrogen flame 6 for heating the optical fiber. The clamps 4 and 5 are connected to a pulling mechanism including a screw rod 22, a guide rod 23, and a drive motor M. The screw bar 22 has left and right opposite threads cut on both sides of one round bar, and is supported by a chassis (not shown) of the apparatus. The screw rod 22 is connected to a drive motor M via a drive transmission mechanism. The clamp 4 is screwed with the right-hand thread of the threaded rod 22, and the clamp 5 is threadedly engaged with the left-hand thread of the threaded rod 22. And clamps 4 and 5
It is slidably engaged with a guide rod 23 supported on the chassis of the apparatus. Further, the apparatus has a light source 7 (wavelength: 1.3 μm) that oscillates a laser beam having a predetermined wavelength, a light amount detector 8, and a light amount detector 9. Further, the screw rod 22 and the guide rod 23 can be removed together with the clamps 4 and 5 from a chassis (not shown) of the apparatus. That is, the clamps 4 and 5, the screw rod 22 and the guide rod 23
Is also a temporary jig for moving to the next step while fixing the mutual positions of the optical fibers that have been fusion-stretched.

In the optical fibers 1 and 2, the protective covering material 3 is previously removed from the portion to be fused, and two places are held by the clamps 4 and 5;
, The output side of the optical fiber 1 is connected to the light amount detector 8, and the output side of the optical fiber 2 is connected to the light amount detector 9. When the drive motor M is rotated after heating the central portion with an oxyhydrogen flame 6 to be in a semi-molten state, the clamps 4 and 5 move outward, respectively, and the optical fibers 1 and 2 are pulled and melted. The optical coupling portion 11 is formed by stretching. At this time, the light quantity detector 8 and the light quantity detector 9 detect the output light quantity from the optical fibers 1 and 2, and extend while checking the branching ratio. As the fusion stretching is performed, the light amount detector 9
(The amount of light output from the optical fiber 2) gradually increases, and conversely, the amount of light detected by the light amount detector 8 (the amount of light output from the optical fiber 1) gradually decreases. When a desired branching ratio (for example, when the light amount detected by the light amount detector 8 and the light amount detected by the light amount detector 9 match, that is, when the branching ratio is 1: 1), the drive motor M is stopped and the oxyhydrogen flame 6 is stopped. To stop fusion stretching.

According to the above process, eight fused and drawn optical fibers 1 and 2 are manufactured, and the branching ratio and excess loss of each fused and drawn product are measured. This process was performed in Examples 2 to 7 and Comparative Example 1.
Table 8 shows the results of measurement of the branching ratio and excess loss as before the bonding and storage.

The screw-shaped rod 22 and the guide rod 23 are removed from the chassis of the apparatus while holding the clamped optical fibers 1 and 2 by the clamps 4 and 5 in the fusion-stretched product obtained by the above-described process. It is sandwiched between protective members 17 of a quartz plate, and is bonded to the front and back of the optical coupling portion 11 with an ultraviolet curing epoxy resin adhesive 16 (one-liquid type or two-liquid type). At this time, the melted and stretched product of the eight optical fibers 1 and 2 was prepared by using the adhesive 16 having a viscosity of 500 cps in Comparative Example 1 and the adhesive 16 having a viscosity of 1000 cps in Example 2.
In Example 3, the adhesive 16 having a viscosity of 5000 cps was used. In Example 4, the adhesive 16 having a viscosity of 10,000 cps was used.
The adhesive 16 having a viscosity of 20,000 cps was used in Example 6.
The adhesive 16 having a viscosity of 0 cps was added to Example 7 by 50,000 cp.
The adhesive 16 having a viscosity of s is bonded and fixed to the comparative example 8 using the adhesive 16 having a viscosity of 187,000 cps. At this point, the clamps 4 and 5 are removed, and the temporary jigs 4 and 5, the screw rod 22 and the guide rod 23 are removed.

Further, the fusion-stretched product of the optical fibers 1 and 2 thus bonded and fixed to the protective member 17 is applied to the protective case 14 (a stainless steel pipe having an outer diameter of 3.3 mm, an inner diameter of 3.0 mm, and a length of 50 mm). Protecting member 17 of quartz plate
The protective case 14 is bonded and fixed with an adhesive 20 (silicone-based adhesive KE45RTV, manufactured by Shin-Etsu Chemical Co., Ltd.), and both ends of the protective case 14 are fixed with the adhesive 20 and sealed. It is completed (see FIG. 1A-A sectional view). At this time, the branching ratio and excess loss of the eight optical fiber couplers of Examples 2 to 7 and Comparative Examples 1 and 8 after the adhesive was stored in the viscosity of the adhesive 16 were measured. The measurement results of the viscosity of each of the adhesives 16 are shown in Table 1 after the adhesion and storage.

Further, after performing a thermal shock test for contracting and expanding the adhesive 16 of the eight optical fiber couplers at -40 ° C. to 85 ° C. five times, Examples 2 to 7 and Comparative Examples 1.8
The branch ratio and excess loss of the eight optical fiber couplers are measured. The measurement results of the viscosity of each adhesive 16 are shown in Table 1 after the thermal shock test.

As a result of the measurement, the viscosity was 500 cps and 1870
In the two optical fiber couplers using the adhesive 16 of 00 cps, the characteristics of the branching ratio and the excess loss were large before and after the adhesive and storage in the protective member 17 and after the thermal shock test. However, the characteristics of the six optical fiber couplers using the adhesive 16 of 1000 to 50,000 cps hardly changed.

The branch ratio and excess loss of an optical fiber coupler are defined by the following equations, respectively.

[0022]

[Formula 1]

P1: light quantity incident on the optical fiber 1 P3: light quantity emitted from the optical fiber 1 P4: light quantity emitted from the optical fiber 2

[0024]

[Table 1]

[0025]

As described above in detail, according to the method for manufacturing an optical fiber coupler of the present invention, the viscosity at 20 ° C. before and after the optical coupling portion is 1000 to 50,000 before and after bonding to the protective member.
Due to the use of the cps adhesive, the characteristics of the branching ratio and excess loss hardly fluctuate before and after the multiple optical fibers are fused and drawn, before and after being housed in the protective member, and after the thermal shock test. However, an optical fiber coupler whose characteristics hardly change can be obtained.

[Brief description of the drawings]

FIG. 1 is a side sectional view and a longitudinal sectional view of an embodiment of an optical fiber coupler manufactured by a manufacturing method to which the present invention is applied.

FIG. 2 is a schematic front view illustrating a process in an example of a method for manufacturing an optical fiber coupler to which the present invention is applied;

[Explanation of symbols]

1 and 2 are optical fibers, 3 is a protective coating material, 4.5 is a clamp, 6 is an oxyhydrogen flame, 7 is a light source, 8.9 is a photodetector, 11
Is an optical coupling part, 14 is a protective case, 16 and 20 are adhesives, 17 is a protective member, 22 is a screw rod, 23 is a guide rod,
M is a motor.

Continuation of the front page (56) References JP-A-63-304206 (JP, A) JP-A-4-46409 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6 / 26 G02B 6/28

Claims (1)

(57) [Claims] 1. A method comprising: bundling a plurality of optical fibers; fusion-stretching a part of the optical fibers while heating them to optically couple them ;
In the method of manufacturing an optical fiber coupler , which is sandwiched between two quartz protective members and bonded and stored, the protective coating material is removed in advance.
A method of manufacturing an optical fiber coupler, comprising bonding an optical fiber before and after an optical coupling portion to a protective member with an adhesive having a viscosity at 20 ° C. of 1000 to 50,000 cps at 20 ° C.